1. Field of the Invention
The present invention relates generally to power over Ethernet (PoE) and, more particularly, to a system and method for using an Ethernet physical layer device (PHY) to identify cabling topologies.
2. Introduction
In a PoE application such as that described in the IEEE 802.3af and 802.3at specifications, a power sourcing equipment (PSE) delivers power to a powered device (PD) over Ethernet cabling. Various types of PDs exist, including voice over IP (VoIP) phones, wireless LAN access points, Bluetooth access points, network cameras, computing devices, etc.
In IEEE 802.3af, a PD may receive power over a single set of two wire pairs from a PSE whether it is a midspan or an endspan. In supporting higher-power applications, additional higher-power PoE specifications can be defined (e.g., IEEE 802.3at) that would allow 2× two wire sets to go out of the same PSE to either an individual PD, which could get double the power, or go to two different PDs.
In general, it is beneficial to find out if multiple sets of wire pairs are going to the same PD. For example, this information can used to establish what a PD may report to the PSE via higher-level protocols. Additionally, this information may also be used to identify that a PD has access to the extra sets of wire pairs for the potential delivery of more power or for power backup. What is needed therefore is a mechanism that enables a power over Ethernet system to identify a cabling topology from the PSE to the PD.